Same file as it's always been in phpBB. Look for overall_header.tpl in the template/ folder of the style.

You can easily add a link if you follow the styling used for one of the default links. Of course, I utilize the a little of the parsers to generate any links and language thing I want to add. Search for {L_SEARCH} and I'm sure the rest is easy.

No longer supporting phpBB. PM or email me regarding support and you will be ignored. I'm fully done with phpBB and everything.